Spot size convertors using InP/InAlAs multiquantum well waveguides for low-loss singlemode fibre coupling

A spot size convertor which consists of an InP/InAlAs multiquantum well core with an InGaAsP tapered core is proposed and demonstrated. This device has a potentially very low coupling loss for singlemode optical fibres and also has a large tolerance in fabrication specifications. A coupling loss to a singlemode fibre of 0.4 dB/facet is obtained.